The present invention relates to a mounting apparatus for mounting a deformable curvature mirror of the type that is capable of controlled deformation by the application of electrical voltages to mirror electrodes on the back side of the mirror with the voltages controlled by the use of a wavefront sensor in an adaptive optics system.
There are various adaptive optics methods and devices which include a wavefront sensor for sensing the aberrations in the wavefront of light waves and then correcting or compensating for those aberrations, such as the atmospheric aberrations that effect the viewing of stars and planets through a telescope. The existing methods and devices for sensing and measuring the wavefront include several interferometric techniques, the Shack-Hartmann wavefront sensing techniques and various other systems involving the projection of patterns of light through an optical system. Such prior techniques and systems are typically complex and expensive, as well as having various inherent deficiencies. In addition to the deficiencies of the prior art wavefront sensors, the deformable mirrors that are controlled by those wavefront sensors for adaptive optics also include numerous deficiencies. For example, the Shack-Hartmann system mirror is comprised of a multiplicity of push rods engaging the back of a flexible mirror and the extension-retraction of each push rod is controlled by the Shack-Hartmann wavefront sensor, but the push rods tend to produce a straight line on the mirror surface between each pair of adjacent push rods that is not truly representative of the curvatures of a wavefront. Moreover, the number of push rods and, therefore, the closeness of the push rods is physically limited, as well as the length of their travel, whereby the accuracy and degree of optical correction that can be applied by the Shack-Hartmann type mirror is limited. Further, some other wavefront sensing and deformable mirror techniques and devices are not directly applicable to all types of adaptive optics for correcting the wavefront to thereby correct the image.
A deformable curvature mirror that solves many of the problems of the prior art deformable mirrors has been developed by the inventors hereof and is the subject of separate, concurrently filed U.S. patent application entitled xe2x80x9cDeformable Curvature Mirrorxe2x80x9d, which mirror is useable in an adaptive optics system having a wavefront sensor described and shown in the copending U.S. patent application Ser. No. 09/579,786, filed May 26, 2000, issued on Sep. 17, 2002, as U.S. Pat. No. 6,452,145, by the inventors hereof. While such deformable curvature mirror and wavefront sensor greatly improve the capabilities of an adaptive optics system, it has been discovered that the mounting of the unique deformable curvature mirror is critical to optimizing the performance of that mirror. Briefly, the deformable curvature mirror of the inventors"" copending patent application is comprised of a laminate of two electro-restrictive disks, such as of PZT material, with a mirrored layer on one side, a pattern of electrodes on the opposite side and an electrically grounded metallic layer sandwiched therebetween, whereby the application of variable electric voltages to the electrodes causes controlled expansion and contraction of the electro-restrictive material to thereby controllably deform the mirror surface. However, since the expansion and contraction of the electro-restrictive material to thereby deform the laminated disks must e precisely controlled, the proper mounting and support of the laminated disks is critical to avoiding undesirable mechanical deformation of the laminated disks during mounting and also to allow the desired deformation of the laminated disks by the applied voltages. Moreover, since the laminated disks of the deformable curvature mirror are subjected to various plating and heating steps, it is virtually impossible to produce a completely flat mounting surface on the mirror from which it can be supported.
In summary, it is an object of the present invention to provide a novel mounting apparatus for a deformable curvature mirror for fixedly supporting a peripheral portion of the mirror between pliable means with means for selectively adjusting the mounting force applied by the pliable means. A further object of the present invention is to provide such a mounting apparatus whereby opposed adjustable means are provided on opposite sides of the peripheral portion of the mirror at a plurality of locations for selectively adjusting the mounting force and direction applied to the mirror perimeter at each such location, including for purposes of mechanically flattening the deformable curvature mirror from its as-manufactured condition. A still further object of the present invention is to provide such a mounting apparatus having a plurality of adjustable screws on opposite sides of the deformable curvature mirror, which screws engage a rubber o-ring on each side of the mirror perimeter for adjustably and firmly mounting the mirror by selectively advancing and retracting individual screws.